@ von Sybe yes you can, you won't have any effects of the mod if the server isn't running it. Sorry you're having trouble... Steam is being a ♥♥♥♥♥ about letting me update the Workshop entry ATM. If you go here: http://forums.tripwireinteractive.com/showthread.php?t=92324you can find a link to an installer which should simplify things

@ von Sybe Unfortunately Unreal Engine can't abide client side mods, so a program like that wouldn't be of use. The mod's files sit unused whenever you aren't in a server running it or you expressly start a game with it enabled under the in-game Workshop section.